The present invention relates to an indwelling catheter, more specifically relates to an indwelling catheter to be left in place in a blood vessel to perform infusion, introduction of a medicinal solution, blood transfusion, blood collection, monitor of blood circulation, etc.
An indwelling needle for use in infusion, transfusion, etc. has a catheter tubing made of a biocompatible, blood-compatible plastic, etc., and is left in a blood vessel with a distal end communicated with a tube extending from a receptacle, such as a infusion bag, containing a fluid, medicinal solution, blood, etc. Some type of the indwelling needle has a sharp-tipped internal needle made of a metal, etc. which longitudinally extends through inside the indwelling catheter and is integrated with the body portion of the indwelling catheter. This type of indwelling needle is inserted into a blood vessel together with the internal needle which is then withdrawn from the catheter to conduct the infusion, transfusion, etc. in the same manner as above.
Since the lumen of the catheter inserted in position in a body cavity must be maintained large enough to effectuate the infusion and introduction of medicinal solution which are the primary use of the indwelling needle, the catheter is required to have a high kinking resistance. Further, the catheter is required to be balanced in stiffness for the insertion into a blood vessel and pliability subsequent to the insertion, because the mechanical properties of the catheter largely affect the puncture of skin, the insertion of the catheter into a body cavity and the injury in wall of blood vessel during the insertion and the emplacement of the catheter.
The catheter used in the conventional indwelling needle has been mainly made of a fluorine resin such as polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, etc. Although, the catheter made of a fluorine resin is sufficiently stiff for ease of the puncture of a skin and the insertion of the catheter into a blood vessel, it does not sufficiently soften in contact with blood. Therefore, there remains a fear of injuring the inner wall of the blood vessel. Also, since such a catheter is insufficient in the kinking resistance, there may be a fear of collapsing the passage for fluid flow.
Recently, a polyurethane resin having a soft segment of polyether has come to be used as the material for the catheter. U.S. Pat. No. 5,226,899 discloses a method of controlling the balance between the stiffness for inserting the catheter into a body cavity and the pliability after the insertion by using a catheter made of a hydrophilic polyetherurethane which softens upon contacting with a body fluid. However, the indwelling catheter made of polyetherurethane does not exhibit a sufficient kinking resistance even after the insertion into a body cavity such as a blood vessel, although it becomes pliable in contact with blood. When the catheter is made stiffer for ease of insertion, the kinking resistance is further deteriorated.